2016ApJ...823..151C

We conducted IRAM-30 m C¹⁸O (2-1) and SMA 1.3 mm continuum ¹²CO (2-1) and C¹⁸O (2-1) observations toward the Class 0/I protostar L1455 IRS1 in Perseus. The IRAM-30 m C¹⁸O results show IRS1 in a dense 0.05 pc core with a mass of 0.54 M_☉, connecting to a filamentary structure. Inside the dense core, compact components of 350 au and 1500 au are detected in the SMA 1.3 mm continuum and C¹⁸O, with a velocity gradient in the latter one perpendicular to a bipolar outflow in ¹²CO, likely tracing a rotational motion. We measure a rotational velocity profile ∝{r}^{-0.75} that becomes shallower at a turning radius of ∼200 au, which is approximately the radius of the 1.3 mm continuum component. These results hint at the presence of a Keplerian disk with a radius M_☉. We derive a core rotation that is about one order of magnitude faster than expected. A significant velocity gradient along a filament toward IRS1 indicates that this filament is dynamically important, providing a gas reservoir and possibly responsible for the faster-than-average core rotation. Previous polarimetric observations show a magnetic field aligned with the outflow axis and perpendicular to the associated filament on a 0.1 pc scale, while on the inner 1000 au scale, the field becomes perpendicular to the outflow axis. This change in magnetic field orientations is consistent with our estimated increase in rotational energy from large to small scales that overcomes the magnetic field energy, wrapping the field lines and aligning them with the disk velocity gradient. These results are discussed in the context of the interplay between filament, magnetic field, and gas kinematics from large to small scales. Possible emerging trends are explored with a sample of 8 Class 0/I protostars.